UL Listed - Safety Certified: Made from non-flammable, self-extinguishing materials. The patented real flange allows the extenders to fit snugly against every style box to assure no gaps are present between the existing box and your newly installed extender. This feature assures that they meet all electrical codes. Universal Fit: Fits any outlet box style, including PVC, Metal, Fiberglass, New Work and Old Work. The most robust outlet extender to exist, working with any kind of box, in situations where traditional boxes may not. 6-32 x 1.25 Screws included!